RAR archive for the MSI MS-6504 board at revision 100, about 598 KB in size. The name does not say what is inside, but MSI archives of this size usually hold a schematic in PDF form. MS-65xx numbers belong to MSI's own desktop motherboard range, so expect a desktop board, not a laptop. Technicians use such a diagram to trace power rails, follow signals and find the parts around a short. Extract it first and check that the revision printed on the PCB matches revision 100 before relying on the values.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @IT_SERVICE_WORLD. Enginerys does not host this file.
How to open a .rar file
Compressed archive — the usual wrapper for a schematic + boardview pair or a BIOS + EC set.